ABSTRACT The vertebrate paleontology, lithostratigraphies, and depositional environments of the Cenozoic continental Titus Canyon and Furnace Creek Formations have been the subjects of several recent investigations. The two units are exposed in the Amargosa Range in northeastern Death Valley National Park, Inyo County, southeastern California, USA. Fossil tracks and trackways are preserved in playa mudflat deposits of the Pliocene Furnace Creek Formation at the Cow Creek tracksite on the western slope of the central Funeral Mountains. The tracksite includes footprints of birds and land mammals, as well as associated sedimentary structures. The lower red beds of the Titus Canyon Formation have produced numerous fossilized bones and teeth at Titus and upper Titanothere Canyons in the southeastern half of the Grapevine Mountains. The fossil remains represent 17 extinct genera and species of land mammals and one genus and species of pond turtle. The taxa constitute the Titus Canyon Fauna. The rodents Quadratomus ? gigans and Dolocylindrodon texanus , the bear dog Daphoenictis n. sp. (small), and the tapir Colodon stovalli are associated elsewhere only in the correlative, late early late Duchesnean Upper Porvenir Local Fauna of Trans-Pecos or Far West Texas. The local fauna occurs in the Blue Cliff Horizon (i.e., above lower marker bed) in the lower part of the Chambers Tuff Formation. The two assemblages share 12 species. The age of the latter unit is constrained by corrected single-crystal laser-fusion 40 Ar/ 39 Ar dates of 37.83 ± 0.09 Ma for the underlying Buckshot Ignimbrite and 37.14 ± 0.08 Ma for the overlying Bracks Rhyolite. However, both determinations should be considered tentative and subject to change with further investigation. The first green conglomerate unit of the Titus Canyon Formation overlies the lower red beds, underlies the Monarch Canyon Tuff Bed, and has produced the first records of land mammal footprints and a land plant (petrified palm wood) from the formation. The Monarch Canyon Tuff Bed and the Unit 38 Tuff Bed, which lies at the mutual tops of the upper “red beds” and the Titus Canyon Formation, are 34.7 ± 0.7 m.y. old and 30.4 ± 0.6 m.y. old, respectively, based on recalculated 40 Ar/ 39 Ar dates. Consequently, the Titus Canyon Formation is latest middle Eocene to earliest Oligocene in age, according to the 2020 Paleogene time scale.

Prepared in conjunction with the 2022 GSA Cordilleran/Rocky Mountain Sections Joint Meeting, this Field Guide showcases trips to geologically interesting areas in Arizona, Nevada, and California. Enjoy a three-day trip to the Buckskin-Rawhide and northern Plomosa Mountains metamorphic core complexes in Arizona. In Nevada, learn about the geology of Frenchman Mountain and Rainbow Gardens and landslide deposits and mechanisms in the eastern Spring Mountains. Or learn about microbialites in Miocene and modern lakes near Las Vegas. When weather permits, unravel the geological history of southern Death Valley, and explore vertebrate paleontology and Cenozoic depositional environments in Death Valley, California.

Abstract Biological soil crusts, composed of soil surfaces stabilized by a consortium of cyanobacteria, algae, fungi, lichens, and/or bryophytes, are common in most deserts and perform functions of primary productivity, nitrogen fixation, nutrient cycling, water redistribution, and soil stabilization. The crusts are highly susceptible to disturbance. The degree of perturbation is governed, at least in part, by the nature, intensity, and spatial and temporal distribution of the disturbance, as well as the soil type and soil moisture content at the time of disturbance. When disturbed, biological soil crusts lose their capacity to perform their ecological functions. Natural recovery of disturbed crusts can range from several years to millennia. Several strategies have been attempted to accelerate recovery of crusts. At present, artificial recovery is not economically feasible on large tracts of disturbed desert landscape. Management options available to the military on arid landscapes include: (1) eliminating or minimizing training in desert ecosystems, (2) avoiding critical seasons, (3) avoiding critical areas, (4) artificially restoring damaged crusts, and (5) considering desert training lands as “sacrifice areas.” Given the need to train in environments representative of the locations of many current and projected world conflicts, the first option is untenable. At this time, the most plausible alternative is to consider desert training lands as “sacrifice areas.” However, it is recommended that attempts be made to avoid critical seasons and areas inasmuch as logistically feasible, and that the military continue to support research into the development of cost-effective technologies for biological soil crust restoration.